Avian Metapneumovirus Infection Rhi ...

Avian Metapneumovirus Infection Rhinotracheitis (Swollen Head Syndrome SHS) in Laying Hens

Avian Metapneumovirus Infection Rhinotracheitis (Swollen Head Syndrome SHS) in Laying Hens

The Avian metapneumovirus infection has been associated with the swollen head syndrome (SHS) in chickens, which is characterized by the following clinical signs: swelling of the periorbital and infra-orbital sinuses, torticollis, cerebral disorientation and opisthotonus, as a result of secondary E coli infection. Usually, less than 4% of the flock are affected, although, widespread respiratory signs are usually present. Mortality rarely exceeds 2%. The infection is associated with reduced egg production loss the shell colour and misshapen eggs. (1, 2)

Avian Metapneumovirus infection in chickens is less clearly defined and may not always be associated with clinical signs. The virus in chickens has been associated with the swollen head syndrome (SHS) in chickens. There is evidence that the infectious bronchitis virus together with E. coli may also associate with SHS. (1, 2)

Observed Clinical Signs Happenings

Egg drop

  • Egg production drops gradually
  • In some cases, egg drop may be not detected

Visibly sick birds

  • Few visibly sick birds
  • Usually, less than 4% of the flock are affected.


  • Low mortality or increases gradually
  • Mortality rarely exceeds 2%

Dead Birds

  • Skinny body (Poor body fleshing condition)


  • Respiratory signs spread fast
  • Widespread respiratory signs are usually present

Neurological /Nervous

  • As a result of secondary E. coli infection
  • Torticollis
  • Cerebral disorientation
  • Opisthotonus

Head Comb Wattles Face Nostrils Sinuses Mount Beak Earlobes

  • Swelling of the Head
  • Swelling of the periorbital and infraorbital sinuses

Body Parts (Neck wings breast abdomen shanks legs hocks feet joints vent skin)

  • Laying hens may also present with prolapsed oviducts due to violent coughing

Shell quality

  • This infection may also affect the quality of eggs
  • Pale or loss of colour in brown-shelled eggs
  • Misshapen eggs


Avian Metapneumovirus Infection Rhinotracheitis (Swollen Head Syndrome SHD) in Laying Hens DOES NOT exhibit or manifest any of the following clinical signs happenings:

  1. Egg production declines rapidly
  2. High mortality or increases rapidly
  3. Dead birds in Good Body fleshing condition
  4. Many visibly sick birds
  5. Flock behaviour activity change
  6. Droppings abnormalities
  7. Respiratory signs spread slow
  8. Lameness or unusual movements, incoordination, ataxia
  9. Eyes abnormalities
  10. Feathers abnormalities
  11. Feed Consumption Changes
  12. Internal Egg defects
Causing Agents
Avian metapneumovirus infection. Avian Metapneumoviruses are members of the subfamily Pneumoviridae, belonging to the family Paramixoviridae
Affected Systems/Organs
Respiratory, Reproductive and Neurological System
Transmission is rapid through aerosols via the respiratory route. Transmission from parents is uncertain. Contaminated objects.
Mainly Affects
Egg production, Egg quality and Liveability
Control respiratory stressors. Multivitamins. Good management practices. Good biosecurity.
Suggested Actions
  • Can be confirmed with clinical signs and gross lesions
  • Can be managed with feed additives, off-the-shelf medications
  • Diagnosis should be confirmed with rapid assays and/or a certified laboratory
  • Veterinary intervention is recommended

Impact on Egg quality


Impact on Liveability


Impact on Production


Overall Economic Impact


  1. Y.M. Saif.2008.Disease of Poultry. 12th Edition. page 103
  2. David E. Swayne. 2013.  Diseases of Poultry 13th Edition. page 115
  3. Mark Pattison, Paul F. McMullin, Janet M. Bradbury. Dennis J. Alexander. 2008. Poultry Diseases. 6th Edition.
  4. Paul McMullin. 2004. A Pocket Guide to Poultry Health and Disease. First Edition.
  5. Steven Leeson, John D. Summers. 2008. Commercial Poultry Nutrition. Third Edition.
  6. Donald D. Bell, Williams D. Weaver. 2009.  Commercial Chicken Meat and Egg Production. Fifth Edition.

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